1. Field of the Invention
This invention relates to an electrophotographic printing machine and more particularly concerns a method for the measurement of a cleaning brush nip width for process control and/or diagnostics as can be used in such a printing machine.
2. Description of the Prior Art
In a typical electrophotographic printing process, a photoconductive member is charged to a substantially uniform potential so as to sensitize the surface thereof. The charged portion of the photoconductive member is exposed to a light image of an original document being reproduced. Exposure of the charged photoconductive member selectively dissipates the charge thereon in the irradiated areas. This records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a developer material into contact therewith. Generally, the developer material comprises toner particles adhering triboelectrically to carrier granules. The toner particles are attracted from the carrier granules to the latent image forming a toner powder image on the photoconductive member. The toner powder image is then transferred from the photoconductive member to a copy sheet. The toner particles are thereafter heated to permanently affix the powder image to the copy sheet. The copy sheets are then sorted and collected into sets of copy sheets. The copy sheets of each set are then secured to one another and stacked for presentation to the machine operator.
In view of the extensive use of toner powder in a typical use of an electrophotographic printing machine, a major issue within an electrophotographic printing apparatus is cleaning. Cleaning within such an apparatus is typically accomplished by the use of a rotating cleaning brush. One of the significant factors in the performance of a cleaning brush in an electrophotographic printing machine environment is the number of brush fiber tips which are available to contact toner entering the zone formed by the interference of the brush to the photoreceptor. The higher the number of available fibers on the brush (fiber strikes) to clean, the better the cleaning and the more robust the cleaner will be to stress inputs and environments. Fiber strikes are a function of the brush diameter, brush speed and brush to photoreceptor interference (i.e. BPI). At any point in time only the speeds and interference can be varied. Over time, however, the diameter of the brush will shrink with usage. This is due to the mechanical set of the brush fibers due to repeated compression in the photoreceptor nip and, if present, detoning roll or flicker bar interferences. Additionally, the brush diameter will decrease due to the accumulation of toner within the brush. (Toner accumulated near the core of the brush holds the fibers in deflected positions.)
Verification of the interference of a new brush to a photoreceptor or to determine the shrinkage of a used brush (and the loss of fiber strikes) is often determined by measuring the width of the cleaning brush nip(s) to the photoreceptor. The nip width was manually measured directly from the photoreceptor surface or from a tape transfer that provided a permanent record of the testing conditions when the brush diameter was known. A simple equation relates the nip width to the brush diameter and the interference, (1/2 Dia.) . sup. 2=(1/2 Dia.xe2x88x92BPI). sup. 2+(1/2 Nip Width). sup. 2. Unfortunately, the present procedure for measuring the nip width procedure is too dirty and complicated to be used as a field service procedure.
It has been proposed to avoid the disadvantages described above to use an ESV or ETAC (BTAC or TAC) sensor to measure the width of the image on the photoconductor surface, i.e. while the image is still in loose particulate toner form. However, an ESV or BTAC sensor looks at only a narrow band around the photoreceptor (BTAC 3 mm and ESV about 12-15 mm).
The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows:
U.S. Pat. No. 5,450,186 to Lundy discloses a flexible cleaner brush belt that increases brush belt life by flexing away from the photoreceptor when not in use. The flexible belt is lifted away from contact with the photoreceptor and placed back into contact with the photoreceptor by a camming device. A camming device attached to linkages, increases the diameter of the flexible brush belt to lift the brush belt away from contact with the imaging surface. The camming device urges the belt brush back into contact with the imaging surface by decreasing the diameter of the brush belt. This movement of the brush belt increases the brush belt life and does not cause print quality defects, excessive toner clouding, or loss of machine productivity.
U.S. Pat. No. 5,381,218 to Lundy discloses a conductive flexible cleaner brush belt having a plurality of detoning stations to remove particles from the brush fibers. At least one of the rollers about which the flexible belt brush is mounted has a small diameter for spreading the brush fibers apart. This spreading of the fibers creates a node affect as the fibers rebound, adjacent fibers open creating a moving node affect. This note affect facilitates detoning of the brush by an air vacuum as air removes the particles from the brush fibers.
U.S. Pat. No. 5,652,945 discloses a method to evaluate the cleaning performance of brush cleaners by measuring the brush to photoreceptor nip width (e.g. cleaning footprint or contact zone) using an ESV sensor or ETAC sensor. This nip width measurement is automatically made using one of the sensing devices and is a measurement of only a portion or part of the width of the loose toner particle image on the photoreceptor. The nip width measurement is converted into diagnostic information using a software algorithm or similar mode of conversion. The diagnostic information can be used in a variety of ways such as a diagnostic tool for a technical representative to warn against the end of brush life, to adjust cleaner biases for automatic changes in setup to achieve better cleaning, to predict brush replacement, to correct brush BPI (i.e. brush to photoreceptor interference) for an under or over engaged brush. In accordance with the advantages of the present invention, transferring the image to paper and fusing the image enables an automated evaluation using a scanner. The advantage of using a scanner is the ability to evaluate the entire width of the cleaner to the photoreceptor interface to find isolated areas of the brushes that have failed or an inboard to outboard variation in the cleaning nip which indicates a possible mechanical problem in controlling a uniform gap between the cleaner and the photoreceptor.
In accordance with the features of the present invention, there is provided a method for measuring a width of a contact zone between a surface, having movement, and a cleaner brush, having a detoning member, the surface having a toner image thereon, the contact zone having particles of the toner image removed from the surface, comprising: developing the toner image on the surface, the toner image having sufficient width to overlap the cleaner brush; moving the toner image to be directly aligned with the cleaner brush; stopping the movement of the surface; rotating the cleaner brush against the surface to remove the toner image from the surface in the contact zone; moving the toner image out of direct alignment with the cleaner brush; transferring the toner image from the surface onto a substrate; fusing the toner image on the substrate; measuring the entire width extending in the process direction of the cleaned areas of the fused image; and converting the measurement of the width for diagnostic analysis and ""process control. Measuring the entire width of the fused image in accordance with the features of the present invention comprises using a scanner for the measurement.